In general, strip chart recorders utilize a strip chart having a sequence of timing grid lines. A problem of such an arrangement is that, although the spacing between successive timing grid lines is precisely determined regardless of the chart speed, there is no way to identify the time interval between adjacent grid lines in the absence of the operator making some notation on the chart as to the time interval of chart timing grid lines. In addition, it is relatively difficult to ascertain from the recording the elapse time between two recorded events since each of the grid lines would have to be counted to arrive at a summation of the elapse time between the recorded events.
Therefore, it is desirable to provide means for coded timing grid lines on the recording charts such that the time interval between successive grid lines is readily ascertained from the chart. In addition, it is desirable to provide means for printing coded time marks corresponding to various increasing intervals of time to facilitate counting of a time interval between two widely spaced events on the recording.